Gas Phase Integrated Multimaterial Printhead for Additive Manufacturing

ABSTRACT

Sputtering printheads, additive manufacturing systems comprising the same, and methods for additive manufacturing are provided. Sputtering printheads of the present invention use a plasma to sputter a feedstock material which is directed towards a target. A printhead can include a heater to heat the feedstock to, or near, the material&#39;s melting point as it is being sputtered to increase the deposition rate. A convergent nozzle can also increase the deposition rate. Printheads of the present invention are readily reconfigurable such that the same printhead can be used to deposit different materials, such as metals and non-metals, in succession by replacing the feedstock material and making changes to a few settings. Additive manufacturing systems of the present invention can be operated at normal room temperatures and pressure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional patent applicationNo. 62/447,388 filed on Jan. 17, 2017 and entitled “Direct Metallic andNon-Metallic Additive Manufacturing using a Sputtering Based RotatingPrint Head at Room Temperatures and Pressures;” this application alsoclaims priority to U.S. provisional patent application No. 62/565,600filed on Sep. 29, 2017 and entitled “Printhead for AdditiveManufacturing of Metals and Ceramics using a Room Temperature BasedMicrosputtering Approach;” this application also claims priority to U.S.provisional patent application No. 62/570,605 filed on Oct. 10, 2017 andentitled “Additive Manufacturing Device Based on MicroelectromechanicalSystem (MEMS) Shutter Array and an Anticlogging Coating;” thisapplication also claims priority to U.S. provisional patent applicationNo. 62/591,198 filed on Nov. 28, 2017 and entitled “AdditiveManufacturing Print Head Based on Liquid Phase Micro-Sputtering Approachand a Nanoparticle Gun for Deposition Rate Enhancement;” each of theaforementioned provisional patent applications are incorporated hereinby reference.

BACKGROUND Field of the Invention

The invention is in the field of additive manufacturing and moreparticularly to a printhead that employs sputtering to deposit metals,ceramics, or plastics.

Related Art

Current methods for metal additive manufacturing (laser-sintering ore-beam melting) require high temperatures to locally melt the material.These manufacturing techniques also have certain limitations includingthe range of compounds they can produce and the consistency andmechanical properties of the desired output. Current approaches to 3Dprinting of metallic objects use high temperatures achieved through theuse a directed energy source, see Bourell, D. L., (2016), Perspectiveson Additive Manufacturing, Annual Reviews of Materials Research, 46(1-18). There are two major approaches for metallic additivemanufacturing, laser sintering of a fine metal powder in a localizedarea, and arc-welding in the region of interest. Both approaches areassociated with high costs, at least ten times the input costs ofconventional manufacturing techniques. Furthermore, the products arecharacterized by inconsistent strengths and a tendency to fracture.These approaches are also limited to materials that can be sintered orarc-welded. For example, semiconductors and oxides can be sputtered butnot arc welded. These impediments slow progress and frustratemanufacturing organizations trying to move from prototyping intoproduction. Babu, S., Love, L. J., Peter, W., and Dehoff R., 2016,Report on Additive Manufacturing for Large Scale Metals Workshop, OakRidge National Laboratory (ORNL), Knoxville Tenn., p. 37(http://info.ornl.gov/sites/publications/files/Pub62831.pdf), andCollins, P. C., Brice, D. A., Samimi, P., Ghamarian, I., Fraser, H. L.,(2016), Microstructure Control of Additively Manufactured MetallicMaterials, Annual Reviews of Materials Research, 46(63).

Further, presently, no single additive manufacturing tool can handleboth electrically conductive and insulating materials. The current stateof the art uses a robot arm to move the part to be manufactured betweena polymer machine, a metallic, and/or a ceramic machine. Currentmetallic additive manufacturing also requires special handling in aninert atmosphere which is free of oxygen and a significant amount ofpost processing after the material is deposited.

SUMMARY

An exemplary additive printhead of the present invention, suitable forprinting 3D objects, comprises a tube attached and aligned with anannular structure. In the exemplary printhead, a gas manifold is influid communication with a first end of the tube, while the opposite endof the tube opens into a central bore of the annular structure. Theannular structure includes a magnet and an electrically conductivematerial, and the bore extends through both. The exemplary printheadfurther comprises a mechanism configured to retain a feedstock materialwithin the tube and further configured to advance the feedstock materialtowards the bore as the feedstock material is consumed. The exemplaryprinthead comprises, further still, a plasma excitation sourceconfigured to create a plasma within the bore of the annular structure.In various embodiments of the exemplary printhead, the printhead furthercomprises the feedstock material, while in other embodiments theprinthead does not include the feedstock material but is configured toreceive the feedstock material.

In various embodiments of the exemplary printhead, the annular structurefurther includes a spacer between the magnet and the conductivematerial, and in some of these embodiments the spacer includes athrough-hole extending radially to the bore to provide fluidcommunication through the spacer to the bore. In further embodiments,the plasma excitation source is a power supply that is configured toprovide the voltage between the feedstock material and the conductivematerial. In some of these embodiments a first electrical connection ismade from the power supply to the conductive material and a secondelectrical connection is made from the power supply to the feedstockmaterial. In some of these embodiments the second connection passesthrough the through-hole in the spacer. In various embodiments, theexemplary printhead further comprises a heater configured to heat an endof the feedstock material proximate to the annular structure, at suchtimes as a feedstock material is being retained by the mechanism. Invarious embodiments, the exemplary printhead further comprises aconvergent nozzle attached to an end of the annular structure oppositeto an end thereof attached to the tube.

An exemplary additive manufacturing system of the present inventioncomprises a sputtering printhead, as just described, and arepositionable stage configured to retain a target proximate to thesputtering printhead. The additive manufacturing system can furthercomprise one or more gas sources in fluid communication with the gasmanifold.

An exemplary method for the additive manufacturing of a 3D objectcomprises at least some of the steps of heating a feedstock materialwithin a printhead, creating a plasma proximate to the feedstockmaterial, also within the printhead, injecting microwave energy into theplasma, advancing the feedstock material, directing the physical vaporonto a target, and replacing the feedstock material to create a secondlayer of the 3D object. These steps can be carried out at about oneatmosphere of pressure and at room temperature. In various embodiments,creating the plasma includes applying an AC or a DC voltage to a gaswithin the printhead. In other embodiments, creating the plasma includesapplying RF energy to the gas within the printhead.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic representation of an additive printing systemaccording to various embodiments of the present invention.

FIG. 2 is a schematic representation of another additive printing systemaccording to various embodiments of the present invention.

FIG. 3 is a schematic representation of still another additive printingsystem according to various embodiments of the present invention.

FIG. 4 is a schematic representation of still another additive printingsystem according to various embodiments of the present invention.

FIG. 5 is a flowchart representation of a method according to variousembodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to sputtering printheads, additivemanufacturing systems comprising one or more of such printheads, andmethods for additive manufacturing. Sputtering printheads of the presentinvention place a material to be sputtered proximate to an annularassembly that includes both an annular magnet and an annularelectrically conductive material. A plasma is produced in a bore of theannular structure, and the material next to one end of the bore issputtered by the plasma, with the sputtered material being expelledthrough the opposite end of the bore to exit the printhead. Inoperation, a gas is directed through the printhead and out through thebore, the plasma is generated from some of the flowing gas within thespace between the conductive layer and the material to be sputtered, andthat plasma then sputters the material. The sputtered material isdirected through the bore by the annular magnet and carried out of thebore and towards the target by the flowing gas. In some embodiments theprinthead includes a heater to heat the material to, or near, thematerial's melting point as it is being sputtered to increase thedeposition rate. A convergent nozzle extending from the end of the borecan also increase the deposition rate. Printheads of the presentinvention are readily reconfigurable such that the same printhead can beused to deposit different materials in succession by replacing thefeedstock material and making changes to a few settings.

Additive manufacturing systems of the present invention comprise one ormore printheads as just described, as well as a repositionable stage orfixture configured to hold a target or substrate onto which a 3D objectcan be manufactured. The repositionable stage comprises translationalmechanisms for moving the target and printhead(s) relative to oneanother to reposition the area of deposition and to maintain a properspacing between the printhead and the 3D object being manufactured.Additive manufacturing systems of the present invention further comprisea control system configured to regulate various parameters such as thegas flow, control the plasma, monitor the deposition rate, control anyheating of the material to be sputtered, and so forth. Additivemanufacturing systems of the present invention can be operated atambient temperatures and pressures and the printheads can be used todeposit both metals and non-metals alike. Some embodiments can depositkilograms of the material per hour.

Methods for additive manufacturing of a 3D object, according to thepresent invention, comprise creating, such as within a printhead, aplasma proximate to a material to be sputtered, and directing sputteredmaterial from the printhead onto a target. The plasma can be created byapplying to a gas any of a DC voltage, an AC voltage, an AC voltage ontop of a DC bias, or by applying radio-frequency (RF) energy in order toionize the gas. Methods of the invention can also comprise advancing thematerial within the printhead as the material is being sputtered. Insome embodiments, methods further comprise heating the material to besputtered to near or to the material's melting point. In furtherembodiments, successive layers of the 3D object are created by replacingone type of feedstock for another, such as replacing a metal feedstockwith a non-metal feedstock in the printhead. Methods can also compriseinjecting microwave energy into the plasma. Methods can also compriseoperating at or near room temperature and/or at normal atmosphericpressures.

FIG. 1 illustrates an exemplary additive printing system 100 of thepresent invention. The system 100 comprises a sputtering printhead 105,a gas supply 110 that provides a gas to the printhead 105, and a stage115 to support a target on which the printhead 105 deposits material.The system 100 further comprises one or more mechanisms (not shown) formoving the stage 115 relative to the printhead 105, which can includemechanisms for translational movements in the X-Y plane, rotationalmovements of the printhead 105 relative to the stage 115, and verticalmovements to vary the spacing between the target and the printhead 105.An exemplary spacing is about 10 mm, but other spacings are employed.Stepper motors and piezoelectric actuators are but two examples ofsuitable mechanisms for these purposes.

It is noted that the system 100 does not have to be operated underreduced pressure, and while a housing may be employed around the system100 to keep out particulates, an enclosure sufficient to maintain avacuum or partial vacuum in the system 100 is not required. As such, thesystem 100 can be operated at normal atmospheric pressure. While notrequired, it is further noted that the system 100 can be placed in avacuum enclosure and operated at pressures below normal atmosphericpressure.

FIG. 1 further provides a schematic cross-section of the sputteringprinthead 105 for additive manufacturing, according to variousembodiments of the present invention. The printhead 105 comprises a tube120 including a feedstock material 125, a gas manifold 130 at one end ofthe tube 120 and an annular structure 135 at the other end of the tube120, the annular structure 135 including a magnet 140 and a conductivematerial 145. A power supply 150 is in electrical communication withboth the conductive material 145 and the feedstock material 125 toproduce a voltage across the space therebetween sufficient to create aplasma of the gas therein.

In operation, an end of the feedstock material 125, which can be in theshape of a rod, for example, is disposed proximate to the annularstructure 135 and sputtered by the plasma and a beam of the sputteredmaterial is expelled through a bore 155 extending through the annularstructure 135 towards a target on the stage 115 onto which the sputteredmaterial is deposited. The printhead 105 can be operated with a widerange of materials for the feedstock material 125, including metals,ceramics, semiconductors, and plastics. In various embodiments, thesystem 100 includes two or more printheads 105 (not shown) that can beoperated alternatingly on a same area, or in parallel on differentareas, of the target. In this way, structures including multipledifferent materials can be fabricated. For instance, several printheads105, each with a different material for the feedstock, can be arrangedin a turret.

The tube 120 of the printhead 105 is a housing that is characterized bytwo ends and a longitudinal axis, and in various embodiments the tube120 is symmetric around that axis, such that a cross-section of the tube120 taken perpendicular to the longitudinal axis is circular, forexample. The tube 120 is capped at one end by the gas manifold 130 andopen at the other end where the tube 120 engages with the annularstructure 135. The tube 120 is hollow so as to accommodate the feedstockmaterial 125 within the tube 120 with sufficient space around thefeedstock material 125 to allow a gas, provided by the gas manifold 130,to flow around the feedstock material 125 and out through the open endof the tube 120 and through the bore 155 in the annular structure 135.The feedstock material 125 can be characterized by a longitudinal axisand can have a cross-section, taken perpendicular to the longitudinalaxis, that is symmetric around the axis, such as circular, for example.In addition to a rod, the feedstock material 125 can additionally takethe form of a disk, a wire, a strip, an ingot, and so forth.

The tube 120 also houses a mechanism 160 that engages with the feedstockmaterial 125 and is configured to retain the feedstock material 125 andadvance it towards the bore 155 as the end of the feedstock material 120is sputtered. Exemplary mechanisms 160 for advancing the feedstockmaterial 125 include a stepper motor and a spring-loaded positioner. Oneor both of the gas manifold 130 or annular structure 135 are readilydetachable from the tube 120 to allow access to the interior of the tube120 to allow for cleaning and for the feedstock material 125 to bereplaced.

The gas manifold 130 is in fluid communication with the end of the tube120 opposite from the annular structure 135 and in further fluidcommunication with the gas supply 110. As noted, this gas is ionizedwithin the printhead 105 and used to sputter material from the feedstockmaterial 125. Suitable gases include both reactive and inert gases,where a suitable inert gases are argon and nitrogen. The gas manifold130 includes a regulator to control the flow of gas into the tube 120,and in various embodiments can have multiple inputs to receive more thanone type of gas from additional gas supplies 110. This can allow morethan one gas to be used at once, but also can allow different gases tobe used with different feedstock materials 125.

As previously noted, the feedstock material 125 is disposed within thetube 120. In some embodiments, the feedstock material 125 is alignedwith the longitudinal axis of the tube 120. “Aligned,” as used herein todescribe two structures, means the structures have longitudinal axesthat are either coaxial or parallel. In some embodiments, a feedstockmaterial 125 made of one material can be readily replaced with afeedstock material 125 made of a different material, and then returnedto operation. As discussed below, changing the material to be depositedmay involve a change to a supplied gas and may involve a change inoperation between an AC, DC, or RF modes, but the printhead 105 itselfis readily adaptable between different deposition materials.

The annular structure 135 includes a magnet 140 and an electricallyconductive material 145. From the cross-sectional view, it can be seethat the magnet 140 and the conductive material 145 form parallel layerswith a gap therebetween. Various embodiments provide an electricallyinsulating spacer 165, such as of plexiglass or acrylic, disposedbetween the magnet 140 and conductive material 145. The annularstructure 135 includes a central bore 155 therethrough, as previouslyindicated, that extends through all of the layers of the annularstructure 135. The annular structure 135 also defines a longitudinalaxis around which the bore 155 and the annular structure 135 are bothsymmetric. The annular structure 135 is attached to the end of the tube120 such that the bore 155 is aligned with the longitudinal axis of thetube 120. This can be achieved where the longitudinal axis of theannular structure 135 is parallel with, or coaxial to, the longitudinalaxis of the tube 120. In one embodiment, the outer diameter of theannular structure 135 is about 75 mm while the diameter of the bore 155is about 19 mm and the thickness of the spacer 165 is about 25 mm.

The annular structure 135 is arranged such that the magnet 140 is closerto the feedstock material 125 than the conductive material 145. In someembodiments the conductive material 145 includes copper. The magnet 140can be, in various embodiments, a permanent magnet such as those thatinclude one or more rare earth elements like samarium. In furtherembodiments the magnet 140 is an electromagnet. The magnetic fieldproduced by the magnet 140 steers and focuses the charged particles thatare sputtered from the feedstock material 125. Exemplary magnets 140suitable for these systems 100 produce on the order of a 1.5T magneticfield.

The spacer 165 can optionally include one or more through-holes 170extending radially through the thickness of the spacer 165. Inembodiments comprising multiple through-holes 170, the holes 170 areoptionally arranged symmetrically around the longitudinal axis of theannular structure 135. As described further below, through-holes 170 canbe used for electrical access, to direct microwaves into the bore 155,or to introduce other gases into the bore 155.

The printhead 105 further comprises a power supply 150 configured toprovide a voltage between the conductive material 145 and the feedstockmaterial 125. The power supply 150 can be switchable to supply either ACor DC, to accommodate sputtering different materials. In variousembodiments the power supply 150 is external to the tube 120 and makesan electrical connection to both the conductive material 145 and thefeedstock material 125 to make the feedstock material 125 into anelectrode and the conductive material 145 into a counter-electrode. Forexample, the feedstock material 125 can be the cathode and theconductive material 145 can be the anode when the power supply 150 isoperated to provide a DC current. The electrical connection between thefeedstock material 125 and the power supply 150 can be passed through athrough-hole 170 and can make a connection to the feedstock material 125with a spring clip or brushes in different embodiments.

In operation, a gas is supplied through the gas manifold 130 and intothe tube 120 which flows around the feedstock material 125 to theannular structure 135 where the electric field between the end of thefeedstock material 125 and the conductive layer 145 ionizes the gas toproduce a localized plasma that sputters the end of the feedstockmaterial 125. The sputtering produces a physical vapor for depositionwhich also becomes charged in the electric field and guided into thebore 155 by the magnet 140. The flowing gas carries the sputtered vaporout through the bore 155 and towards the target. At atmosphericpressure, the plasma of the sputtered material tends to stayconcentrated in a filament.

FIG. 2 illustrates another exemplary additive printing system 200 of thepresent invention. System 200 replaces the power supply 150 of FIG. 1with an RF source 210 that provides radio-frequency energy to the gas toproduce the sputtering plasma. RF source 210 and power supply 150 aretwo examples of plasma excitation sources. Some systems of the presentinvention include both a power supply 150 and an RF source 210 and canbe readily switched between them, or can employ both simultaneously.

FIG. 3 illustrates another exemplary additive printing system 300 of thepresent invention. System 300 adds to the system 100 both a heater 310for raising the temperature of an end 320 of the feedstock material 125nearest the annular structure 135, and a convergent nozzle 330 attachedto an end of the annular structure 135 furthest from the feedstockmaterial 125. Heater 310 can employ induction to produced localizedheating in the end 320, in some embodiments. In various embodiments, theheater 310 comprises an RF coil disposed around the outside of the tube120.

In certain embodiments, the heater 310 is used to raise the temperatureof the end 320 to, or near to, the melting point of the material. Forexample, the temperature can be raised to within 5% of the melting pointas measured in degrees Kelvin. In further embodiments, the feedstockmaterial 125 comprises a material that is a mixture of two or moresubstances, such as a metallic alloy, and in some of these embodimentsthe composition of the mixture constitutes a eutectic, which is thecomposition with the lowest melting point of all possible compositionsfor a mixture of those substances. As such, eutectic compositionsrequire less heating to reach the eutectic temperature, and also meltcompletely at the eutectic temperature. Sputtering at or near themelting point of a material can enhance deposition rates (e.g. 0.5 to 1kilograms per hour for metals and 1.5 to 2 kilograms per hour forceramics). Where the end 320 is heated to near melting, less energy isneeded to dislodge material. Therefore, a plasma applied to a materialat or near melting will sputter more material than the same plasmaapplied to the same material but well below the melting point.

Deposition rates can be further increased by using the convergent nozzle330. By converging, the nozzle 330 increases the velocity and decreasespressure which has the effect of condensing the emitted target materialinto larger nanoparticles before deposition

FIG. 4 illustrates still another exemplary additive printing system 400of the present invention. System 400 adds to the system 100 a microwavesource 410 configured to provide microwave power into the bore 155.Microwave power can be introduced though the through-hole 170 frommicrowave source 410, which can be a 2.45 GHz source, for example. Themicrowave frequency can optionally be adjusted, as well as the peakpower. In some embodiments, a suitable power range extends from a fewwatts to 3 kilowatts.

The microwave source 410 is coupled into the bore 155 by a waveguide420. The waveguide 420 is basically a hollow metallic cylinder. Additionof the microwave source 410 helps to produce a high and uniform plasmawith very high electron density which assists in rapid and uniformmaterial deposition. It is noted that the various features of the heater310, nozzle 330, and microwave source 410 can be used in anycombination, though shown in separate drawings.

As noted, through-holes 170 in the spacer 165 can also be used todeliver reactive gases into the bore 155. Such gases includeorganosilane, hydrogen, acetylene, tungsten hexafluoride,triisobutylaluminum, and related pentachloride gases for depositingmetals. These gases can also, or in the alternative, be introduced alongwith the carrier gas through the gas manifold 130.

FIG. 5 provides a flowchart representation of an exemplary method 500 ofthe present invention. The method 500 is directed to the additivemanufacturing of a 3D object and comprises an optional step 510 ofheating a feedstock material within a printhead, and a step 520 ofcreating a plasma proximate to the feedstock material and also withinthe printhead, where the plasma sputters the feedstock material toproduce a physical vapor. The method 500 also comprises an optional step530 of injecting microwave energy into the plasma, an optional step 540of advancing the feedstock material, and a step 550 of directing thephysical vapor onto a target. Method 500 can further comprise a step 560of replacing the feedstock material to create a second layer of the 3Dobject. The steps of method 500 are shown in FIG. 5 as sequential but itwill be understood that various steps may be performed together oriteratively, for instance, the steps 510-550 can all be performedsimultaneously in some embodiments. These steps can also be carried outat ambient temperatures and at or around one atmosphere pressure.

In step 510 the feedstock material is heated by a heater, for example byan RF coil disposed outside of the printhead and positioned proximate toa sputtering zone within the printhead. In various embodiments, the stepincludes heating the feedstock material to within 5% of the material'smelting point, or to the melting point. The step can also includemonitoring the temperature of the feedstock material with an infra-red(IR) sensor, for example, and controlling the power to the heater with acontroller. Proportional-integral-derivative (PID) controls may be usedfor this and other feedback controls used herein.

In step 520 a plasma is created within the printhead proximate to thefeedstock material in order to sputter the feedstock material to producea physical vapor. This step can include flowing a gas through theprinthead. Creating the plasma can include, depending on the material tobe sputtered, applying a DC voltage to the gas within the printhead, anAC voltage to the gas, or RF energy to the gas. Step 520 can alsoinclude adding a reactive gas to the system, either along with a carriergas through a gas manifold, or separately via a through-hole in thespacer.

In step 530 microwave energy is optionally injected into the plasma,such as from a microwave source via a waveguide. In various embodiments,the microwaves are supplied at a frequency of 2.45 GHz, as one example.The step can include varying the frequency and peak power. In someembodiments, a suitable power range extends from a few watts to about 3kilowatts.

In step 540 the feedstock material is advanced within the printhead asthe feedstock material is being sputtered. This can include controllinga mechanism configured to advance the feedstock material, such as astepper motor. This can also include controlling the rate at which thefeedstock material is advanced, such as based on the deposition rate.The rate can also be controlled based on measuring the capacitancebetween the feedstock and the conductive material 145, or by opticalmeans to measure the distance to the feedstock material.

In step 550 the physical vapor is directed onto a target to produce afirst layer of the 3D object. Directing the physical vapor onto thetarget can include magnetically steering the physical vapor, as well aspassing the vapor through a convergent nozzle. This step can alsocomprise repositioning a stage supporting the target while the physicalvapor is directed onto the target, as well as continuously controllingthe position of the target and separation between the printhead and thetarget.

In step 560 a second layer of the 3D object is created. In this step thefeedstock material is replaced with another so the second layer iscompositionally different from the first layer of the 3D object. Step560 can include opening the printhead, removing the existing feedstockmaterial, replacing a new feedstock material of a different composition,and closing the printhead. The step can also comprise switching a modeof operation between any one of DC, AC, and RF to create the plasma in anext iteration of step 520. For instance, DC can be used with conductivefeedstocks like metals, AC and RF can be used on non-metals likeceramics, semiconductors, and plastics.

The descriptions herein are presented to enable persons skilled in theart to create and use the printheads and additive manufacturing systemsand methods described herein. Various modifications to the embodimentswill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other embodiments andapplications without departing from the spirit and scope of theinventive subject matter. Moreover, in the following description,numerous details are set forth for the purpose of explanation. However,one of ordinary skill in the art will realize that the inventive subjectmatter might be practiced without the use of these specific details. Inother instances, well known machine components, processes and datastructures are shown in block diagram form in order not to obscure thedisclosure with unnecessary detail. Identical reference numerals may beused to represent different views of the same item in differentdrawings. Flowcharts in drawings referenced below are used to representprocesses. A hardware processor system may be configured to perform someof these processes. Modules within flow diagrams representing computerimplemented processes represent the configuration of a processor systemaccording to computer program code to perform the acts described withreference to these modules. Thus, the inventive subject matter is notintended to be limited to the embodiments shown, but is to be accordedthe widest scope consistent with the principles and features disclosedherein.

The use of the term “means” within a claim of this application isintended to invoke 112(f) only as to the limitation to which the termattaches and not to the whole claim, while the absence of the term“means” from any claim should be understood as excluding that claim frombeing interpreted under 112(f). As used in the claims of thisapplication, “configured to” and “configured for” are not intended toinvoke 112(f).

What is claimed is:
 1. A sputtering printhead for additivemanufacturing, the printhead comprising: a tube including a longitudinalaxis, a first end, and a second end, the tube being open at the secondsend; a gas manifold in fluid communication with the first end of thetube; a mechanism configured to retain a feedstock material within thetube and further configured to advance the feedstock material towardsthe bore; an annular structure including a magnet and an electricallyconductive material, the annular structure having a central boretherethrough and attached to the second end of the tube such that thebore is aligned with the longitudinal axis and the magnet is closer tothe mechanism than the conductive layer; and a plasma excitation sourceconfigured to create a plasma within the bore of the annular structure.2. The sputtering printhead of claim 1 further comprising the feedstockmaterial.
 3. The sputtering printhead of claim 1 wherein the annularstructure further includes a spacer between the magnet and theconductive material.
 4. The sputtering printhead of claim 3 wherein thespacer includes a through-hole extending radially to the bore.
 5. Thesputtering printhead of claim 1 wherein the plasma excitation sourcecomprises a power supply configured to provide a voltage through a firstelectrical connection to the conductive material and a second electricalconnection to the feedstock material.
 6. The sputtering printhead ofclaim 5 wherein the annular structure further includes a spacer betweenthe magnet and the conductive material, the spacer includes athrough-hole extending radially to the bore, and the second connectionpasses through the through-hole.
 7. The sputtering printhead of claim 1wherein the plasma excitation source comprises an RF source.
 8. Thesputtering printhead of claim 1 further comprising a heater configuredto heat an end of the feedstock material proximate to the annularstructure when the feedstock material is retained by the mechanism. 9.The sputtering printhead of claim 8 wherein the heater comprises an RFcoil disposed around the tube proximate to the annular structure. 10.The sputtering printhead of claim 1 further comprising a convergentnozzle attached to a side of the annular structure opposite to a sidethereof attached to the tube.
 11. The sputtering printhead of claim 3further comprising a microwave source configured to inject microwavesinto the bore via the through-hole.
 12. An additive manufacturing systemcomprising: a sputtering printhead including a tube including alongitudinal axis, a first end, and a second end, the tube being open atthe second send, a gas manifold in fluid communication with the firstend of the tube, a mechanism configured to retain a feedstock materialwithin the tube and further configured to advance the feedstock materialtowards the bore, an annular structure including a magnet and anelectrically conductive material, the annular structure having a centralbore therethrough and attached to the second end of the tube such thatthe bore is aligned with the longitudinal axis and the magnet is closerto the mechanism than the conductive layer, and a plasma excitationsource configured to create a plasma within the bore of the annularstructure; and a repositionable stage configured to retain a targetproximate to the sputtering printhead.
 13. The additive manufacturingsystem of claim 12 further comprising a gas source in fluidcommunication with the gas manifold.
 14. A method for the additivemanufacturing of a 3D object, the method comprising: heating a feedstockmaterial within a printhead to at least 5% of a melting point of thefeedstock material; creating, within the printhead, a plasma proximateto the feedstock material in order to sputter the feedstock material toproduce a physical vapor; and directing the physical vapor from theprinthead onto a target to produce a first layer of the 3D object. 15.The method of claim 14 further comprising injecting microwave energyinto the plasma.
 16. The method of claim 14 further comprising operatingat about one atmosphere of pressure.
 17. The method of claim 14 furthercomprising advancing the feedstock material within the printhead as thefeedstock material is being sputtered.
 18. The method of claim 14further comprising creating a second layer of the 3D object by removingthe feedstock material from within the printhead and replacing thefeedstock material with a different feedstock material.
 19. The methodof claim 14 wherein creating the plasma includes applying a DC voltageto a gas within the printhead.
 20. The method of claim 14 whereincreating the plasma includes applying an AC voltage to a gas within theprinthead.
 21. The method of claim 14 wherein creating the plasmaincludes applying RF energy to a gas within the printhead.